1. Field of the Invention
The present invention relates generally to hand trucks for facilitating the conveying, loading and unloading of cargo, and more particularly to a hand truck with an electrically operated lifting platform, which is capable of lowering the costs of manufacture and maintenance and improving convenience in handling and safety.
2. Description of the Prior Art
In general, in order to convey, load and unload massive cargo, a plurality of pillars and rails are arranged in a factory and a hoist is mounted so as to be moved along the rails.
However, this kind of arrangement necessitates high installation costs, has lower rapidity and inconvenient working procedure to convey relatively small cargo, and requires to use separate conveying means and lifting means in an area outside of the area over which rails are extended.
On the meantime, a hydraulic pallet truck is proposed so as to convey, load or unload cargo to which the hoist cannot be applied or is not easily applied. In the hydraulic pallet truck, two wheels are rotatably attached to both sides of the lower end of the frame, a stabilizing plate is forwardly extended from the lower end of the frame, a handle is formed at the upper end of the frame, and a lifting mechanism is mounted to the frame.
The lifting mechanism is comprised of two forks attached to the frame to selectively lift up and lower down cargo while supporting the cargo, a hydraulic drive unit to drive the forks, and a control unit to control the operation of the lifting mechanism. In the lifting mechanism, the forks are moved upward and downward along the frame by the action of the hydraulic drive unit through the control of the control unit, and, accordingly, cargo placed on the forks is lifted up and lowered down with the movement of the forks.
However, the conventional hydraulic pallet truck is expensive and relatively heavy because its hydraulic drive unit and control unit should be provided, and causes inconvenience to a user because its forks cannot be brought into contact with the ground owing to the large mounting space of hydraulic drive unit and should be supported by a support.
Additionally there is proposed another hand truck with a lifting fork unit, in which a square screw shaft is rotatably and vertically supported by a frame, a drive motor is mounted on the lower portion of the frame and connected to the screw shaft, and a lifting fork unit is engaged with the screw shaft to be vertically moved along the screw shaft. Accordingly, the screw shaft is rotated by the operation of the drive motor, the lifting fork unit is selectively lifted up and lowered down by the rotation of the screw shaft, and cargo is selectively lifted up and lowered down by the movement of the lifting fork unit.
However, the conventional hand truck has inferior safety because their screw shafts are exposed to the outside, and is costly because its rapid ascent control unit and drive unit are expensive.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a hand truck with an electrically operated lifting platform, in which a lifting platform is attached to a frame provided at its lower ends with wheels to be moved selectively upward and downward, and a platform moving unit is situated in the lifting platform to be controlled by a drive control unit, thereby having a simple structure, being manufactured at lower costs and obtaining the same output as that of a conventional hand truck.
In order to accomplish the above object, the present invention provides a hand truck with an electrically operated lifting platform, comprising; a frame on both sides of which two guide rails are formed, the frame being provided with a screw shaft vertically supported on the frame to be vertically moved, one or more stabilizing bars forwardly extended from the frame and two wheels rotatably attached to the rear portion of the frame; a lifting platform guided by the guide rails and engaged with the screw shaft; a platform moving unit comprised of a first drive motor for providing rotating force, said platform being situated in the lifting platform to allow the lifting platform to be moved selectively upward and downward along the screw shaft by the operation of the first drive motor; and a control unit electrically and controllably connected to the first drive motor and a power source.